java util NoSuchElementException - Scanner reading user input

Question

I m new to using Java  but I have some previous experience with C   The issue I m having comes with reading user input from console   I m running into the  java util NoSuchElementException  error with this portion of code   payment   sc next       PromptCustomerPayment function   I have two functions that get user input    PromptCustomerQty PromptCustomerPayment   If I don t call PromptCustomerQty then I don t get this error  which leads me to believe I am doing something wrong with scanner  Below is my full code sample  I appreciate any help    public static void main  String   args               Create a customer        Future proofing the possabiltiies of multiple customers     Customer customer   new Customer  Will            Create object for each Product         Name Code Description Price         Initalize Qty at 0     Product Computer   new Product  Computer   PC1003   Basic Computer  399 99        Product Monitor   new Product  Monitor   MN1003   LCD Monitor  99 99       Product Printer   new Product  Printer   PR1003x   Inkjet Printer  54 23           Define internal variables            DONT CHANGE      ArrayList lt Product gt  ProductList   new ArrayList lt Product gt        List to store Products     String formatString     -15s  -10s  -20s  -10s  -10s  n      Default format for output         Add objects to list     ProductList add Computer       ProductList add Monitor       ProductList add Printer           Ask users for quantities      PromptCustomerQty customer  ProductList           Ask user for payment method     PromptCustomerPayment customer           Create the header     PrintHeader customer  formatString           Create Body     PrintBody ProductList  formatString         public static void PromptCustomerQty Customer customer  ArrayList lt Product gt  ProductList           Initiate a Scanner     Scanner scan   new Scanner System in                VARIABLES          int qty   0          Greet Customer     System out println  Hello     customer getName             Loop through each item and ask for qty desired     for  Product p   ProductList             do              Ask user for qty         System out println  How many would you like for product      p name           System out print   gt                  Get input and set qty for the object         qty   scan nextInt                       while  qty  lt  0      Validation          p setQty qty      Set qty for object         qty   0     Reset count               Cleanup     scan close       public static void PromptCustomerPayment  Customer customer           Initiate Scanner      Scanner sc   new Scanner System in           Variables     String payment               Prompt User     do       System out println  Would you like to pay in full   Yes No         System out print   gt           payment   sc next           while    payment toLowerCase   equals  yes     amp  amp    payment toLowerCase   equals  no              Check set result     if  payment toLowerCase       yes             customer setPaidInFull true             else           customer setPaidInFull false                 Cleanup     sc close

User · Answer

You need to remove the scanner closing lines  scan close    It happened to me before and that was the reason

User · Answer

This has really puzzled me for a while but this is what I found in the end   When you call  sc close   in first method  it not only closes your scanner but closes your System in input stream as well  You can verify it by printing its status at very top of the second method as        System out println System in available       So  now when you re-instantiate  Scanner in second method  it doesn t find any open System in stream and hence the exception   I doubt if there is any way out to reopen System in because   public void close   throws IOException -- gt  Closes this input stream and releases any system resources associated with this stream  The general contract of close is that it closes the input stream  A closed stream cannot perform input operations and   cannot be reopened     The only good solution for your problem is to initiate the Scanner in your main method  pass that as argument in your two methods  and close it again in your main method e g    main method related code block   Scanner scanner   new Scanner System in         Ask users for quantities  PromptCustomerQty customer  ProductList  scanner        Ask user for payment method PromptCustomerPayment customer  scanner       close the scanner  scanner close      Your Methods    public static void PromptCustomerQty Customer customer                                ArrayList lt Product gt  ProductList  Scanner scanner            no more scanner instantiation                no more scanner close       public static void PromptCustomerPayment  Customer customer  Scanner sc            no more scanner instantiation                no more scanner close      Hope this gives you some insight about the failure and possible resolution

User · Answer

The problem is     When a Scanner is closed  it will close its input source if the source implements the Closeable interface    http   docs oracle com javase 1 5 0 docs api java util Scanner html  Thus scan close   closes System in   To fix it you can make  Scanner scan static and do not close it in PromptCustomerQty   Code below works   public static void main  String   args           Create a customer    Future proofing the possabiltiies of multiple customers Customer customer   new Customer  Will        Create object for each Product     Name Code Description Price     Initalize Qty at 0 Product Computer   new Product  Computer   PC1003   Basic Computer  399 99    Product Monitor   new Product  Monitor   MN1003   LCD Monitor  99 99   Product Printer   new Product  Printer   PR1003x   Inkjet Printer  54 23       Define internal variables        DONT CHANGE  ArrayList lt Product gt  ProductList   new ArrayList lt Product gt        List to store Products String formatString     -15s  -10s  -20s  -10s  -10s  n      Default format for output     Add objects to list ProductList add Computer   ProductList add Monitor   ProductList add Printer       Ask users for quantities  PromptCustomerQty customer  ProductList       Ask user for payment method PromptCustomerPayment customer       Create the header PrintHeader customer  formatString       Create Body PrintBody ProductList  formatString         static Scanner scan   public static void PromptCustomerQty Customer customer  ArrayList lt Product gt  ProductList                     Initiate a Scanner scan   new Scanner System in            VARIABLES      int qty   0      Greet Customer System out println  Hello     customer getName         Loop through each item and ask for qty desired for  Product p   ProductList         do          Ask user for qty     System out println  How many would you like for product      p name       System out print   gt              Get input and set qty for the object     qty   scan nextInt               while  qty  lt  0      Validation      p setQty qty      Set qty for object     qty   0     Reset count       Cleanup     public static void PromptCustomerPayment  Customer customer       Variables String payment           Prompt User do   System out println  Would you like to pay in full   Yes No     System out print   gt       payment   scan next       while    payment toLowerCase   equals  yes     amp  amp    payment toLowerCase   equals  no          Check set result if  payment toLowerCase       yes         customer setPaidInFull true     else       customer setPaidInFull false         On a side note  you shouldn t use    for String comparision  use  equals instead

User · Answer

the reason of the exception has been explained already  however the suggested solution isn t really the best  You should create a class that keeps a Scanner as private using Singleton Pattern  that makes that scanner unique on your code  Then you can implement the methods you need or you can create a getScanner   not recommended   and you can control it with a private boolean  something like alreadyClosed  If you are not aware how to use Singleton Pattern  here s a example  public class Reader                 private Scanner reader      private static Reader singleton   null      private boolean alreadyClosed           private Reader             alreadyClosed   false          reader   new Scanner System in                  public static Reader getInstance             if singleton    null                singleton   new Reader                      return singleton                 public int nextInt   throws AlreadyClosedException           if  alreadyClosed                return reader nextInt                      throw new AlreadyClosedException      Custom exception                public double nextDouble   throws AlreadyClosedException           if  alreadyClosed                return reader nextDouble                      throw new AlreadyClosedException                   public String nextLine   throws AlreadyClosedException           if  alreadyClosed                return reader nextLine                      throw new AlreadyClosedException                   public void close             alreadyClosed   true          reader close

[java] java.util.NoSuchElementException - Scanner reading user input

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